The present invention relates to an ultrasonic motor wherein piezoelectric vibration members are laminated one upon another and, more particularly, to an improvement of a type of ultrasonic motor that uses no retaining means when the piezoelectric vibration members are laminated. The present invention also relates to an electronic apparatus having the ultrasonic motor.
Recently, attention has been drawn, in the field of a micromotor, toward an ultrasonic motor wherein a moving body is moved using a piezoelectric vibrator that vibrates due to the application of a voltage.
Particularly, an ultrasonic motor that uses a stretching vibration and a flexing vibration of a rectangular piezoelectric vibrator (dual-mode vibrator) is used for various purposes because this synthetic vibration is used to cause straight-line movements, rotary movements, etc. of a moving body. Further, piezoelectric vibrators which are laminated are also used in devices which require a high output (see Japanese Patent Application Laid-Open Publication No. Hei-7-184382).
FIG. 10 illustrates a type of ultrasonic motor wherein rectangular piezoelectric vibrators are laminated.
Namely, a basic vibrator of the ultrasonic motor is comprised of piezoelectric oscillators 61 and 62 with respect to which a prescribed polarization processing is performed for vibrating each of them in two modes, output taking members 71 and 72 which have been provided at forward ends of the piezoelectric oscillators 61 and 62, and electrodes which have been provided on both surfaces of each of the piezoelectric oscillators 61 and 62. The piezoelectric oscillators 61 and 62 are stacked vertically in three stages and arranged laterally in two rows, and these six piezoelectric vibrators are retained by connecting means 67a and 67b.
FIG. 11 is a block diagram illustrating a basic structure of the above-described ultrasonic motor.
According to this structure, the piezoelectric oscillators 61 and 62 are dual-mode vibrated by being applied with a voltage from electrode patterns 81 and 82, respectively, this synthetic vibration is transmitted to each of the respective output taking members 71 and 72, and a moving body 21 is moved which is kept in abutment with the output taking members 71 and 72.
By this construction, since the output is taken out from a plurality of the output taking members 71 and 72, a high output is obtained.
However, according to the above-described ultrasonic motor, since respective parts of the piezoelectric oscillators 61 and 62 are only fixed by the connecting means 67, there exists the technical problem that a vibration-directional dispersion occurs between the respective piezoelectric oscillators 61 and 62 and also, since the vibration movements are suppressed at the respective fixed portions of the piezoelectric oscillators 61 and 62, a loss of the vibration movement occurs with the result that the output cannot be taken out effectively.
Furthermore, when the connecting means 67 which is a separate member is used for fixing the piezoelectric oscillators 61 and 62, the construction of the entire motor becomes undesirably large in size and complex and, since the step of mounting the connecting means 67 is added, the manufacturing process becomes complex.
Meanwhile, in the respective piezoelectric oscillators 61 and 62, each of which makes its dual-mode vibrations, a voltage is applied to prescribed polarization processed portions thereof for the purpose of changing over the movement direction of the motor through the flexing vibrations. Therefore, there exists the technical problem that the stretching vibrations which are incidentally caused cannot be enlarged compared to the flexing vibrations which are forcedly caused.